Bottom-hole electric heater



April 2, 968 D.' MIRCEA 3,376,403

BOTTOM-HOLB ELECTRI C HEATER Filed NOV. l2, 1964 IIVENTOR om. GA Mmc A WMU/@W ATTORN EY United States Patent 3,376,403 ROTTGM-HOLE ELECTRIC HEATER Drig Mircea, Cimpina, Rumania, assignor to Ministerul Petrolului, Bucharest, Rumania Filed Nov. 12, 1964, Ser. No. 410,682 4 Claims. (Cl. 219-10.49)

ABSTRACT F THE DISCLOSURE A bottom-hole electric heater comprising a plurality of conductors of preferably spiral shape which are encased in temperature resistant material and extend through a corresponding number of pipes of ferro-magnetic material. When an inductive current passes through the conductors heat energy is produced in the pipes due to the Joule losses caused by the eddy currents induced in the pipes.

The pipes also protect the conductors encased therein from damage while the bottom-hole heater is in the well casing.

The present invention relates to an electric bottomhole heater for stimulating oil production in an oil bearing strata.

Various electric heater types are known for downhole heating of oil production wells.

The most commonly used is the three-phase electric bottom-hole heater type which comprises three spiral elements which act as resistive conductors, the latter are inserted and secured in chamotte (reclay) insulating tubes, which are, subsequently lled with a chamotteclay-water-sodium silicate mixture and, after the mixture has dried, the conductors are sealed in a pressure resistant assembly consisting of three metal pipes.

The heat energy supplied by these heater types is not uniform, as the point of direct heat dissipation is thermally insulated from the medium to which the heat is to be supplied by the immobile air layer present between the steel pipe walls and the insulating tubes as well as by the chamotte layer. This requires a substantially higher temperature in the resistive conductors, due to the high temperature drop across the thermal insulation.

In addition thereto the drying process requires a long period of time and considerable heat consumption; and chemical reactions between some substances contained in the chamotte and the resistive conductors may also occur, which sometimes causes the resistive conductors to break during the manufacturing process or leads to early failures while in operation.

Another known bottom-hole heater type which eliminates the above described disadvantages brought about by drying, uses precalcinated chamotte .powder instead of the wet mixture. However heat conduction is still poor in this known device and its manufacturing process is complicated.

It is a general object of this invention to provide a bottom-hole heater which eliminates all of the disadvantages of the aforedescribed prior art devices. The bottomhole heater of this invention comprises one or more pipes made of ferromagnetic material. The pipes may have various shapes and contain axially extending insulated conductor Wherethrough the inductive current flows. The heat produced by the Joule losses due to the eddy currents induced in the pipes is directly supplied to the fluid in the producing oil well, which contacts directly the body of the heater.

These and other features and advantages of the present invention will become further apparent from the following detailed description thereof which is to be read with reference to the accompanying drawing, in which:

The bottom-hole heater according to the invention comprises three pipes 1, 2, 3, of spiral shape. Each pipe includes an axially extending conductor 4, said conductor being insulated from the pipe by means of a temperature resistant material 5 (glasslibre stocking, aluminum oxide or magnesium oxide, porcelain heads).

The ends of the three pipes 1, 2, 3, are mounted in the connecting part 6, and the conductors 4 extend through the insulating parts 7 and 8 and end either at the terminals 9, to which the supply line is connected, or at the terminals 10 which effect a three phase star connection.

The connecting part 6 includes a tapered threaded portion 11 for connecting the heater to the power cable stuing-box assembly, which is identical to the ones employed for bottom-hole heaters presently in use.

When an energizing voltage is supplied to the bottomhole heater inductive currents are produced which by creating eddy currents in the pipe bodies cause heat energy to be produced by the Joule effects.

The heat energy is directly supplied to the surrounding uid, which in turn transfers it to the producing well section.

In order to prevent the transformation elect from giving rise to an appreciable potential dilierence, between the turns of the heater, the turns are welded together, either directly by welding beads 12, or by longitudinal bands.

The advantages of the present invention are as follows: f

A highly eicient heat transfer by conduction is effected. The device of this invention can be simply and inexpensively manufactured.

Although my inventionv has been illustrated and described with reference to the preferred embodiments thereof, I wish to have it understood that it is in no way limited to the details of such embodiment but is capable of numerous modifications within the Scope of the appended claims.

What is claimed is:

1. An electric bottom-hole heater, comprising in combination, a connecting member, a plurality of electrical terminals mounted in said connecting member, a plurality of electrical conductors being connected to said plurality of electrical terminals and projecting from said connecting member, a corresponding plurality of pipes of ferromagnetic material being mounted in said connecting member and projecting therefrom, each pipe of said plurality of pipes being coaxial with and surrounding a corresponding conductor of said plurality of conductors, whereby when said plurality of electrical terminals are connected to a source of electric power the current axially ilowing through said plurality of electrical conductors induces eddy currents in said plurality of pipes and, consequently, heat energy is produced in said plurality of pipes by means of the Joule effect.

2. The electric bottom-hole heater as set forth in claim 1, including heat resistant insulating material disposed in each pipe between the conductors extending therethrough and the interior walls of the corresponding surrounding pipe.

3; The. electric bottom-hole heater as set forth in claim 2,302,774 11/ 1942 Jarrsy 'y 219410.51 1Wherein said 'plurality of pipes and said plurality of 2,472,445 6/1949 Sprong 219-278 X conductors are of mating spiral configuration. 3,071,675 l/1963 Cronberger 2l9-10.51

4. The electric bottom-hole heater as set forth in claim 1,989,582 l/ 1935 Becker et al. 219-10-49 1, wherein said plurality of pipes are pressure resistant 5 2,635,168 4/ 1953 Lerza et al 2l9-10.49 and thereby protect said plurality of conductors which 2,977,454 3/ 1961 Volker 2l9-336 are disposed therein.

References Cited y UNITED STATES PATENTS 2,229,630 1/1941 somes 219-1079 1G RICHARD M. WOOD, Primary Examiner.

L. H. BENDER, Assistant Examiner. 

